Expression and Distribution of Claudins in Crohn's Disease

Aim: There is an impaired intestinal barrier function in patients with Crohn's disease. Recent reports suggest that this may be attributed to the altered expression of tight junction proteins. The aim of our current research is to investigate expression levels of several tight junction proteins from claudin family in colon tissue resections of patients with Crohn’s disease. Patients and Methods: Colonic tissue specimens of patients with active Crohn’s disease were used for the RT-qPCR and immunohistochemical analysis. Resection borders from tumor colectomy were used as controls. Total RNA was isolated from formalin-fixed paraffin-embedded tissue samples. RNA was reverse transcribed using random hexamers and SuperScript III First-Strand synthesis system. Gene expression was analyzed by RT-qPCR using the TaqMan method and glycerin-aldehyde-3-phosphate (GAPDH) as a housekeeping gene. Results were expressed as relative fold change using averaged control samples as calibrator. Expression and localization of claudins were also evaluated by immunohistochemical analysis. In addition, claudin expression was correlated with Th1 (e.g. IFNg and IL-12p40) and Th17 (e.g. IL-17) cytokine expression and clinical data.

Results: Enhanced expression of Claudin-1 and -2 was observed in patients with Crohn’s disease. On the other hand, expression of Claudin-4 and -8 was not statistically different between the two groups of patients.

Conclusion: The results of this study point to difference in selective expression and localization of claudins in colonic tissue of patient’s with Crohn’s disease and controls, in relation to different expression of pro-inflamamtry cytokines.